screenshots probably will help (crop to the area showing the applet icons in XFCE and then what you see in unity)
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fossfreedom♦Apr 20 '13 at 8:01

I believe you don't need screenshots. Consider I receive an error about the notification area selection: "The notification area lost selection. Most likely another widget took over the function of a notification area. This area will be unused."
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jasminesApr 20 '13 at 13:11

2 Answers
2

Probably those icons are related to something in notification area.
In Unity notification area is already handled by another indicator, and the one in xfce4-panel (or whatever else) would conflict. That's why the second loaded notification area will always fizzle.